Intervalometer



J. J. NASH INTERVALOMETER Nov; 10,1970

Filed Dec. 31, 1968 4 Sheets Snee'L 1 INVENTOR N 1% N ATTORN EY Nov. 10, 1970 J. J. NASH 3,539,955

IN TERVALOMETER Filed Dec. 31,- 1968 4 Skwetsoneex 2 Jon-1N J. NASH m MW ATTORN EY J. J. NASH INTERVALOMETER Nov. 10,- '1970 4 Sheets-Snem 3 Filed Dec. 31, 1968 INVENTOR sa y- ATTORNEY J. J. NASH INTERVALOMETER Nov. 10, 1970 4 dimers-sneer 4.

' Filed Dec. 31, 1968 INVENTOR JOHN NASH WE w ATTORNEY United States Patent 3,539,955 IN TERVALOMETER John J. Nash, Ferguson, Mo., assignor to Alsco, Inc., St. Louis, Mo., a corporation of Delaware Filed Dec. 31, 1968, Ser. No. 788,227 Int. Cl. HOlh 51/08 US. Cl. 335-138 Claims ABSTRACT OF THE DISCLOSURE An intervalometer comprises a connector means adapted to be electrically connected to a source of electricity, a solenoid in electrical connection with the connector means, a plurality of output terminals, a distributor tab adapted to move to each of the output terminals, and switch means between the connector means and the distributor tab. The switch means is movable from an open position wherein the distributor tab is electrically disconnected from the connector means to a closed position wherein the distributor tab is electrically connected to the connector means. Mechanism responsive to the actuation of the solenoid .is adapted to cause the switch to move to its closed position and to cause the distributor tab to move to each of the output terminals. Biasing means yieldably maintains the switch in its open position so that the distributor tab and the output terminals are electrically disconnected from the connector means whenever the solenoid is deactivated.

This invention relates to intervalometers and more particularly to intervalometers adapted for use on rocket launchers.

Rocket launchers used by US. military forces are comprised of a bundle of cylindrical tubes which slidably receive rockets and which are suspended beneath aircraft. The rockets are fired by the introduction of electrical current to an ignition cap at the rear end of each rocket. The electricity is introduced from a power source through an intervalometer which directs the current to each ignition cap of each rocket one at a time. Intervalometers in the present state of the art are adapted to be set for single firing and ripple firing. In single firing the intervalometer directs current to one rocket each time the airplane pilot closes a switch in the cockpit. In ripple firing the intervalometer is initially actuated by the closing of the switch in the cockpit and then it automatically causes the rockets to fire one at a time in successive order until they are all fired.

Intervalometers comprise a solenoid adapted to move a distributor mechanism leading to a plurality of output terminals to introduce electricity to them one at a time. The output terminals each are electrically connected to ignition terminals in electrical contact with the ignition caps of each rocket. As the distributor makes contact with each output terminal it introduces a jolt of electricity to each ignition terminal, thereby setting off the ignition caps and firing the rockets one at a time. The ignition terminals are usually metal contacts which engage the ignition caps of the rockets. They are insulated from the rocket launching tubes so that there will be no short circuiting of the circuit from the power source to the ignition cap of the rockets. Occasionally, however, the rocket launching tubes become bent or distorted and come in contact with the ignition terminals, thereby short circuiting the electrical circuit to the rocket ignition caps and preventing firing of the rocket in that particular tube. Short circuiting also occurs when the ignition terminals themselves become bent or damaged. When this happens not only does the rocket fail to fire, but the grounded ignition terminals short circuit the circuit from the power source to the solenoid of the intervalometer. As a result the inter- Patented Nov. 10, 1970 valometer stops'and does not complete its cycle to all of the terminals. For example, if the ignition terminal of the second rocket happens to be short circuited, the intervalometer will progress to that particular terminal and then will stop without completing the remainder of the cycle. 1

Among the several objects of the present invention may be noted the provision of an intervalometer which will step over any grounded output terminal and will progress on to the other terminals; the provision of an intervalometer wherein the power source is connected to the output terminals only after the solenoid is actuated; the provision of an intervalometer wherein the output terminals are all grounded except when fired to prevent the buildup of stray voltage and static electricity; the provision of an intervalometer which includes an interrupter switch which alternatively directs current to the solenoid and to the output terminals; the provision of an intervalometer wherein the circuit from the power source to the solenoid is isolated from they output terminals to prevent short circuiting when the output terminals are grounded; the provision of an intervalometer including a distributor mechanism and a grounding mechanism secured to the same rotating member to deliver electricity to individual output terminals while simultaneously grounding the remaining output terminals; and the provision of an intervalometer which is durable in use and economical to manufacture. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a perspective view of the intervalometer;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is an exploded perspective view of the structure shown in FIG. 4;

FIG. 6 is a detailed perspective view of the interrupter mechanism;

FIG. 7 is a perspective view of the bottom surface of the upper wafer shown in FIG. 5; and

FIG. 8 is a schematic diagram of the electrical circuit showing the electrical interconnection of the various components of the intervalometer.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the drawings, 10 designates a housing assembly having an upper housing 12 and a housing base 14. Upper housing 12 includes three lateral sides 16, 18, 20, and one end flange 22. End flange 22 has a switch slot 24 forming communication between the outside of housing assembly 10 and the interior thereof. Two horizontal bracket lips 26, 28, extend from the exterior face of end flange 22. A grounding tab 30 having a yoke portion 32 is secured to bracket lips 26, 28, by means of a cotter pin 34 extending vertically through the arms of yoke 32 and bracket lips 26, 28. Yoke 32 is permitted to pivot about the vertical axis created by cotter pin 34. At the opposite end of grounding tab 30 from yoke 32 is an aperture 36 with a wing stud 38 extending therethrough. Wing stud 38, grounding tab 30, and cotter pin 34 are all constructed of material which is a good electrical conductor, the purpose of wing stud 38 being to make grounding connection with a conventional rocket launcher (not shown). A spring element 40, also constructed of a good electrical conducting material, is coiled about cotter pin 34 and has its opposite ends extending through switch slot 24 into the interior of upper housing 12.

Housing base 14 consists of a bottom 42, a first vertical end 44 adjacent end flange 22 of upper housing 12, and two spaced apart vertical legs 46, 48, on the end of housing base 14 opposite from first vertical end 44. Housing base 14 is constructed of a material which is a good electrical conductor and is secured to upper housing 12 by screws 50, as illustrated in FIG. 3. It should be noted that first end 44 is adjacent end flange 22, but that spring element 40 is embraced therebetween. The result is that spring element 40* forms electrical connection between housing base 14 and grounding tab 30. A slide switch 52 having a slide button 54 is secured to the inside of first end 44 'with slide button 54 extending outwardly through an aperture in first end 44 and through switch slot 24 in end flange 22. Thus slide button 54 may be moved from the outside of housing 10. Slide button 54 is movable between a single fire position and a ripple fire position.

A connector member 56 is secured to housing base 14 by bolts 58, 60, extending through vertical legs 46, 48, of housing base 14. Bolts 58, 60, are constructed of a good electrical conducting material and extend through connector member 56 to form electrical connection with male guide pin 62 and female guide pin 64, respectively. Guide pins 62, 64, are ground-leads and are adapted to be connected by wires to a ground. Also extending through connector member 56 are a plurality of connector pins C. These connector pins C are shown schematically in FIG. 8 and include ten rocket connector pins C -C an input connector pin C and a solenoid connector pin C FIGS. 4 and illustrate a deck assembly within housing 10. Two vertical guide posts 66, 68, are rigidly secured to housing base 14 and extend upwardly therefrom. A pivot aperture 70 extends through housing base 14 and is centered between guide posts 66, 68. A movement member 72 is pivotally mounted within pivot aperture 70 and includes a bearing poriton 74 extending through aperture 70, a ratchet wheel 78 directly above and adajacent to housing base 14, and a vertically disposed center post 80 extending upwardly from ratchet wheel 78. Center post 80 is rectangular in cross-section. A ratchet spring plate 82 having wings 84, 86, on opposite sides of a bearing portion 88 is positioned over ratchet wheel 78 with guide posts 66, 68, extending through apertures in wings 84, 86, and center post 80 extending through an aperture in bearing portion 88. Bearing portion 88 includes two downwardly projecting catch fingers 90, 92, which bear against ratchet wheel 78. Catch fingers 90, 92, are adapted to be received yieldably within each of a plurality of apertures 94 arranged in a circular array in ratchet wheel 78. Thus while ratchet Wheel 78 may be turned by the application of a substantial torque thereto, fingers 90, 92, tend to hold ratchet wheel 78 against rotational movement. In addition, because of the slanting position of fingers 90, 92, ratchet wheel 78 can turn in only one direction. As ratchet wheel 78 rotates, fingers 90, 92, snap in and out of apertures 94, thereby causing ratchet wheel 78 to progress a step at a time.

An interrupter switch 95 is mounted on a crescentshaped dielectric interrupter deck 96 which has its crescent tips slidably received over guide posts 66, 68, directly over and adjacent to ratchet spring plate 82. Interrupter switch 95 includes a first fixed interrupter terminal 97 and a second fixed interrupter terminal 98. First interrupter terminal 97 has a first fixed contact point 99, and second fixed interrupter terminal 98 has a second fixed contact point 100. A movable interrupter terminal 102 is also secured to interrupter deck 96 and has a spring arm 104 extending therefrom with a movable contact point 106 on its end between first and second fixed contact points 99, 100. Spring arm '4 yieldably holds movable contact point 1.06 against first fixed contact point 99. Also on spring arm 104 is a cam follower shoulder 108. First fixed terminal 97, second fixed terminal 98, movable terminal 102, spring arm 104, and fixed and movable contact points 99, 100, 106, are all made of a material which is a good electrical conductor.

Directly above interrupter deck 96, a pivot plate 110 is slidably mounted on guide posts 66, 68, which extend through apertures on its opposite sides. Pivot plate 110 includes a cylindrical pivot collar 112 extending upwardly therefrom with center post extending upwardly through its interior. A cam 114 is rotatably received over pivot collar 112 by means of a center aperture 116. Cam 114 includes a cam finger 118 on one side thereof and first and second drive lips 120, 122, on opposite sides thereof. FIG. 6 illustrates the interrelationship of cam 114 and interrupter deck 96 when the components are assembled. Cam finger 118 abuts against cam follower shoulder 108 of spring arm 104. Thus the rotation of cam 114 causes cam finger 118 to push against cam follower shoulder 108, thereby pushing movable contact point 106 away from first fixed contact point 99, and causing it to be moved into electrical contact with second fixed contact point 100.

Directly above cam 114 is a top spring plate 124 which is slidably received over guide posts 66, 68, and which has an aperture 126 in the center thereof with center post 80 extending upwardly therethrough. A pair of shims 128, 130, are slidably received over guide posts 66, 68, respectively, to help urge top spring plate 124 downwardly against cam 114. Cam 114 has a plurality of ball bearings 132 which are suflicient in diameter to extend both above and below the upper and lower surfaces of earn 114 to allow cam 114 to move freely with respect to pivot plate and top spring plate 124.

Directly above shims 128, 130, is a lower deck wafer 134 which has a center aperture 136 therein (FIG. 4). Rotatably received Within center aperture 136 is a diskshaped lower deck bearing 138 made of dielectric material and having a rectangular keyhole 139 therein for receiving center post 80 of movement member 72. A flange 140' is provided on the bottom of lower deck bearing 138 and engages the lower surface of lower deck wafer 134 to limit the upward axial movement of lower deck bearing 138 within center aperture 136. A solenoid control mechanism 142 is mounted on the upper surface of lower deck wafer 134 and includes a solenoid control ring 144 having a notch 146 therein, a power terminal 148, and a plurality of solenoid terminals 150. Solenoid control ring 144 is secured to the upper surface of lower deck bearing 138 by means of prongs 151 extending through lower deck bearing 138. Flange 140 and solenoid control ring 144 embrace the opposite surfaces of lower deck wafer 134 so as to hold lower deck bearing 138 against axial movement within center aperture 136. Power terminal 148 is secured to lower deck wafer 134 and is positioned so that it engages solenoid control ring 144 at all times except when notch 146 is adjacent it. When notch 146 is positioned adjacent power terminal 148 the electrical connection between solenoid control ring 144 and power terminal 148 is broken. Solenoid terminals 150, however, extend inwardly toward the inner edge of solenoid control ring 144 a suflicient distance so that they are always in electrical contact with solenoid control ring 144 regardless of the position of notch 146. Power terminal 148 is adapted to be connected to a power source and solenoid terminals 150 are adapted to he connected to a solenoid. Electrical current from power terminal 148 will be conducted through solenoid control ring 144 to solenoid terminals 150 as long as power terminal 148 is in electrical connection with solenoid control ring 144. However, the circuit from the power source to solenoid terminals 150 can be broken by moving notch 146 adjacent power terminal 148.

Slidably received on guide posts 66, 68, directly above lower deck wafer 134 are two additional shims 152. Slida bly received over guide posts 66, 68, directly above shims 152 is an upper deck assembly 154 which includes an upper deck wafer 156 having a center aperture 158 therein. Rotatably received within center aperture 158 is a discshaped dielectric upper deck bearing 160 which includes a rectangular aperture 162 extending upwardly from its bottom surface and terminating short of its upper surface for receiving the extreme upper end of center post 80. The top of upper deck bearing 160 is formed into the shape of a triangular pointer 163 and a screw driver slot 164 which are adapted to protrude through an aperture in upper housing 12 so that they are visible and accessible from outside housing 10 (FIG. 1).

Referring to FIGS. 4 and 7, a distributor ring 166 is operatively secured to the bottom surface of upper deck bearing 160 by means of prongs 168. A distributor power terminal 170 is secured to the bottom surface of upper deck wafer 156 and is adapted to be continually in contact with distributor ring 166. Distributor power terminal 170 is also in electrical connection with second fixed contact 100. On the upper surface of upper deck bearing 160 (FIG. is a grounding mechanism 172 which includes a circular grounding ring 174 secured to the upper surface of upper deck bearing 160 by prongs 176. Grounding ring 174 includes a cutout portion or notch 177. A distributor tab 178 is secured to upper deck bearing 160 in the space provided by notch 177 and includes connecting prongs 179 (FIG. 4), which extend downwardly through upper deck bearing 160 and are in contact with distributor ring 166, thereby providing an electrical connection between distributor ring 166 and distributor tab 17 8. Grounding ring 174 is insulated from distributor tab 178 and distributor ring 166 because its prongs 176 are embedded in the dielectric material of upper deck bearing 160.

A plurality of output terminals T -T are arranged in a circular array and secured to the upper surface of upper deck wafer 1156 so that they are in electrical contact with the outer edge of grounding ring 174. Two grounding terminals G and G are also included in this circular array. Output terminals T -T are electrically connected to connector pins C C which in turn lead to ignition terminals I -I respectively, as illustrated in FIG. 8. Grounding terminals G and G are electrically connected either to guide pin 62 or guide pin 64 which are in turn adapted to be grounded so that grounding terminals G and G are always electrically grounded. Not-ch 177 of grounding ring 174 is of a width that disconnects one terminal at a time as grounding ring 174 rotates throughout one revolution. Thus, grounding ring 174 is in electrical connection with all but one of the output terminals T -T and grounding terminals G and G Because of this arrangement at least one of the grounding terminals G and G is always in electrical contact with grounding ring 174 and consequently all of the output terminals in contact with grounding ring 174 are grounded. Thus, grounding ring 174 grounds all of the output terminals while notch 177 breaks electrical connection between grounding ring 174 and each of the output terminals T T one at a time. Because distributor tab 178 is positioned in the space provided by notch 177 it simultaneously makes electrical contact with the same terminal which is disconnected from grounding ring 174 by notch 177. Thus, as upper deck bearing 160 rotates through one revolution, each of the output terminals is simultaneously disconnected from grounding ring 174 and connected to distributor tab 178 at one time.

When ratchet wheel 78 is rotated it also rotates center post 80, lower deck bearing 138, and upper deck bearing 160. Solenoid control ring 144 rotates in unison with lower deck bearing 138. Rotating with upper deck bearing 160 are distributor ring 166, distributor tab 178, and grounding ring 174. The keying of center post 80 to lower deck bearing 138 and upper deck bearing 160 causes all these units to rotate in unison. The center apertures in the other components of the deck assembly are sufficiently large to permit free rotation of center post 80.

Referring to FIGS. 2 and 3, a solenoid 180 is operatively secured to housing base 14 adjacent the previously described deck assembly. Solenoid 180 includes a solenoid rotor .182 which is adapted to rotate upon activation of solenoid 180. A link or drive arm 184 is pivotally secured to solenoid rotor 182 at one of its ends and has the other of its ends slidably received through a slide bracket 186 which is operatively secured to housing base 14. A spring stop 188 is on the end of drive arm 184 opposite solenoid rotor 182 and a coil spring 190 is positioned around drive arm 184 between spring stop 188 and slide bracket 186 to yieldably urge drive arm 184 to the left as viewed in FIG. 2. Slide bracket 186 holds drive arm 184 so that its intermediate portion is adjacent the deck assembly. An L- shaped spring 192 (FIG. 6) is operatively secured at one of its ends to drive arm 184 with a downwardly projecting pawl or drive finger 194 at its opposite end and extending downwardly through an aperture in drive arm 184 to engage the teeth of ratchet wheel 78 (FIG. 6). Drive arm 184 is also equipped with an upwardly projecting pawl or drive finger 196 which is disposed between drive lips 122, of cam 114. Thus, as viewed in FIG. 6, upon activation of solenoid drive arm 184 is moved to the right, thereby causing downwardly projecting finger 194 to rotate ratchet wheel 78 in a counterclockwise direction and causing upwardly projecting drive finger 196 to engage drive lip 122 of cam 114 to rotate cam 114 in a counterclockwise direction. The rotation of cam 114 in a counterclockwise direction causes cam finger 118 to bear against cam follower shoulder 108, thereby moving movable contact point 106 from first fixed contact point 99 to second fixed contact point 100. Upon deactuation of solenoid 180'. drive arm 184 is returned to its original position by coil spring 190. As spring moves drive arm 184 to the left as viewed in FIGS. 2 and 6, upwardly projecting finger 196 strikes drive lip 120 and rotates cam 114 in a clockwise direction. This rotation permits spring arm 104 to move movable contact 106 back into electrical contact with first fixed contact, 99.

Referring to the schematic drawing of FIG. 8, a plurality of pairs of rocket ignition terminals I I and a single rocket ignition terminal I are positioned adjacent nineteen rockets R. Rockets R are all grounded to the rocket launcher L as a result of their engagement with the rocket launching tubes in which they are placed. Each of the rocket ignition terminals I I are electrically connected to connector pins C -C which are in turn electrically connected to output terminals T T The method of operation is as follows: Triangular pointer 163 is manually positioned pointing to load Which is marked on the outer surface of upper housing 12 as viewed in FIG. 1. In this position the various components are positioned as follows: Solenoid control ring 144 is positioned with its notch 146 adjacent power terminal 148, thereby freeing power terminal 148 from electrical contact with solenoid control ring 144. Distributor tab 178 and notch 177 of grounding ring 174 are positioned at grounding terminal G In this position the outer peripheral edge of grounding ring 174 is in electrical contact with grounding terminal G and with all of the output terminals T T Thus in the load position all of the ignition terminals I I are grounded to drain off any stray voltage. Whenever the device is in the load position there is no danger of accidental firing caused by a voltage potential building up on any one of the ignition terminals 1 4 When the rocket launcher is to be prepared for firing, triangular pointer 163 is manually rotated to the position marked arm on the outer surface of housing 10 as viewed in FIG. 1. In this position solenoid control ring 144 is positioned with its notch 146 slightly counterclockwise with respect to power terminal 148. Thus power terminal 148 is in electrical contact with solenoid control ring 144 and electrical connection from a power source 198 through input connector C and power terminal 148 into the system is prevented only by an operator switch 200 which is normally located in the cockpit of the airplane. In the arm position the distributor tab 178 and notch 177 are positioned adjacent grounding terminal G thereby leaving distributor tab 178 free from electrical contact with any of the output terminals T -T and maintaining all the output terminals T T in electrical contact with grounding ring 174.

Before the airplane takes off, slide switch 52 is positioned in either the single fire position or the ripple fire position. In the single fire position, slide switch 52 is closed, and in the ripple fire position it is open. The method of operation when the slide switch is in the ripple fire position is as follows: When the pilot wishes to fire a rocket he closes operator switch 200, thereby completing an electrical circuit from power source 198 through operator switch 200, through input connector pin 0,, through power terminal 148, through solenoid control ring 144, through solenoid terminal 150, through movable terminal 102, through spring arm 104, through first fixed terminal 97, through solenoid 180 to activate it, and through solenoid connector pin C which is connected to a ground.

The activation of solenoid 180 causes drive arm 184 to be moved to the right, causing downward projecting finger 194 to rotate ratchet wheel 78 and causing upward projecting finger 196 to meet drive lip 122 of cam 114, thereby rotating'cam 114. The effect of this movement is that movable contact 106 is pushed out of electrical contact with first fixed contact point 99 during activation of solenoid 180. However, because slide switch 52 is open, the movement of movable contact 106 away from first fixed contact 99 causes the circuit from the power source to solenoid 180 to be broken, thereby deactuating solenoid 180'. When solenoid 180 is deactuated drive arm 184 is again returned to its original position by coil spring 190, thereby causing 114 to return to its original position, and permitting spring arm 104 to urge movable contact 106 back into electrical contact with first fixed contact 99. Solenoid .1 80 is again actuated and the cycle repeats itself, solenoid 180 being actuated and deactuated alternatively. This alternative actuation and deact-uation causes two movements.

The first movement is the reciprocal movement of movable contact 106 from a first position in electrical contact with first fixed contact 99 to a second position in electrical contact with second fixed contact 100. This causes electric current to be alternatively directed first to solenoid 180 and next through distributor ring 166 and prongs 179 to distributor tab 178. The second movement produced by solenoid 180 each time it is actuated is a stepwise rotary movement of ratchet wheel 78 caused by the reciprocation of drive arm 184 and downwardly projecting finger 194. The stepwise rotation of ratchet wheel 78 causes distributor tab 178 to step around from one output terminal to another. The movement of movable contact 106 and distributor tab 178 is coordinated so that current is introduced to distributor tab 17 8 each time it moves into contact with another terminal. Thus as distributor tab 178 steps around it causes current to be introduced to each of the ignition terminals I -I so that the rockets will be fired one pair at a time. The stepping action automatically continues until solenoid control ring 144 returns to its original position and notch 146 causes power source 198 to be cut off from solenoid 180 permanently.

If slide switch 52 is in a closed position the breaking of electrical contact between movable contact point 106 and first fixed contact point 99 causes the electrical circuit to be diverted from movable terminal 102 through slide switch 52 to solenoid 180, thereby maintaining solenoid 180 in an activated state and consequently maintaining movable contact point 106 in its second position away from first fixed contact point 99. The only way to alternatively activate and deactivate solenoid 180 is to open and close operator switch 200, thereby opening and cutting off power source 198 from the system. Thus a system is provided which permits the firing of rockets one at a time with each opening and closing of operator switch 200.

This construction provides a result heretofore not obtained in intervalometers for rocket launchers. The output terminals T -T and the ignition terminals are never connected to power source 198 until after the actuation of solenoid 180. Consequently they cannot short circuit the circuit between power source 198 and solenoid 180. If, for example, ignition terminal I were grounded, distributor tab 178 would move from output terminal T to output terminal T and would simultaneously introduce a jolt of electricity to output terminal T The grounding of ignition terminal I would prevent the firing of the third rocket, but it would not prevent distributor tab 178 from progressing further. Spring arm 104 instead would urge movable contact 106 into its first position where it is disconnected from distributor tab 178 and where it reestablishes the circuit from the power source to solenoid 180. As a result solenoid 180- continues to be alternatively actuated and deactuated to cause distributor tab 178 to step on through its cycle, thereby firing all the remaining rockets.

Notch 177 in grounding ring 174 releases ignition terminals I -I from grounding contact one at a time simultaneously with the introduction of electrical current from power source 198 for firing. The gorunding mechanism causes all of ignition terminals I -I to be grounded at all times except during their intended firing. The grounding contact caused !by grounding ring 174 prevents misfiring of ignition terminals I -I during the firing cycle and during the time that triangular pointer 178 is in either the load or arm position.

Another important feature of this invention is the provision of a housing which includes three avenues for grounding electrical current from the ground-leads formed by bolts 58, 60. Grounding is accomplished by direct electrical connection of guide pins 62, 64, with a conventional ground. Grounding is also accomplished from bolts 58, 60, through housing base 14, through the rocket launcher which engages housing base 14, to the grounded airplane. The third avenue is from bolts 58, 60, through housing base 14, through spring element 40, through grounding tab 30, to the rocket launcher.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

What is claimed is:

1. An intervalometer comprising connector means adapted to be electrically connected to an electrical source of current; a solenoid in electrical connection with said connector means and adapted to be actuated by the introduction of electrical current, a plurality of output terminals; a distributor tab adapted to move to each of said output terminals to make electrical contact with said output terminals one at a time; switch means between said connector means and said distributor tab, said switch means being movable from an open position wherein said distributor tab is electrically disconnected from said connector means to a closed position wherein said distributor tab is electrically connected to said connector means; mechanism responsive to the actuation of said solenoid to cause said switch means to move to its closed position and to cause said distributor tab to move to each of said output terminals one at a time; and biasing means yieldably maintaining said switch in its open position so that said distributor tab and said output terminals are electrically disconnected from said connector means whenever said solenoid is deactuated.

2. The intervalometer of claim 1 wherein said switch means includes first and second fixed contacts and a movable contact, said movable contact being connected in series with said solenoid and said connector means, said movable contact being free from electrical contact with said second fixed contact when said switch means is in its open position, said movable contact being in electrical contact with said second fixed contact when said switch means is in its closed position.

3. The intervalometer of claim 2 wherein said first fixed contact is in electrical connection with said solenoid; said movable contact engaging said first fixed contact when said switch means is in its open position.

4. The intervalometer of claim 1 wherein said plurality of output terminals are positioned in a circular array on a dielectric wafer and said distributor tab is rotatable to each of said output terminals.

5. An intervalometer comprising a dielectric wafer, a plurality of output terminals in circular array on said water; a grounding mechanism electrically connected to a ground and rotatably mounted on said water, said mechanism including a grounding portion in electrical contact with said output terminals and a circuit breaker means adapted to rotate to each of said output terminals one at a time to disconnect said output terminals from said grounding portion; a distributor tab rotatably mounted on said wafer and adapted to rotate to each of said output terminals in unison with said circuit breaker means so that their rotation causes each of said output terminals to be disconnected from said grounding portion and simultaneously to be connected to said distributor tab; means for introducing electrical current to said distributor tab from a power source so that electrical current will be conducted to the one of said output terminals in contact with said distributor ta'b; a prime mover adapted to be actuated by electrical current; and mechanism responsive to the actuation of said prime mover to cause said circuit breaker means and said distributor tab to rotate to each of said output terminals.

6. The intervalometer of claim 5 wherein said means for introducing electrical current to said distributor tab is a switch electrically connected to a connector means, said connector means being adapted to be connected to an electrical power source and said switch means being movable from an open position wherein said distributor tab is disconnected from said connector means to a closed position wherein said distributor tab is electrically connected to said connector means.

7. The intervalometer of claim 5 wherein said means for introducing electrical current to said distributor tab is an interrupter switch connected in series between said prime mover and a power source; said interrupter switch having a first position connecting said power source to said primer mover and a second position connecting said power source to said distributor tab.

8. The intervalometer of claim 7 wherein a biasing means yieldably holds said interrupter switch in its first position; said mechanism including means responsive to actuation of said prime mover to cause said interrupter switch to move to its second position.

9. The intervalometer of claim 5 wherein a bearing means is rotatably mounted on said wafer and said grounding mechanism, said distributor tab being secured to said bearing means.

10. An intervalometer comprising a stationary assembly including a dielectric wafer; a plurality of output terminals arranged in circular array on said wafer; a dielectric bearing rotatably mounted to said stationary assembly; a grounding mechanism mounted on said bearing and electrically connected to ground, said grounding mechanism being adapted to rotate with said bearing from an initial position wherein it is in electrical contact with all of said output terminals through a plurality of positions wherein it breaks electrical contact with each of said output terminals one at a time; a distributor tab mounted on said bearing and adapted to rotate there- 'with through a plurality of positions wherein it makes electrical contact with each of said output terminals; the relative position of said distributor tab and said grounding mechanism on said dis'k being such that each of said output terminals is simultaneously disconnected from said grounding mechanism and connected to said distributor tab; means for introducing electrical current to said distributor tab; and drive means for rotating said bearing.

11. An intervalometer comprising a plurality of output terminals; a distributor tab adapted to move to each of said output terminals one at a time; a prime mover adapted to be actuated by electrical current; an interrupter switch connected in series between said prime mover and a power source; said interrupter switch being movable from a first position connecting said power source to said prime mover to a second position connecting said power source to said distributor tab; biasing means yieldably holding said interrupter switch in its first position to prevent electrical connection between said power source and said distributor tab; and mechanism responsive to the actuation of said prime mover to cause said interrupter switch to move to its second position and to cause said distributor tab to move to each of said output terminals.

'12. An intervalometer according to claim 11 wherein said interrupter switch includes two fixed contacts and a movable contact; said movable contact engaging one of said fixed contacts when said interrupter switch is in its first position and engaging the other of said fixed contacts when said interrupter switch is in its second position.

13. An intervalometer according to claim 12 wherein said biasing means is a spring arm and said movable contact is mounted on said spring arm.

14. An intervalometer according to claim 11 wherein said mechanism includes a link connected to and driven by said prime mover; said link including means for moving both said distributor tab and said interrupter switch in response to actuation of said prime mover.

15. An intervalometer according to claim 11 wherein said distributor tab is rotatable about a first axis and said mechanism includes a cam and a link; said cam being rotatable about said first axis and said link being drivingly connected to said prime mover; said link including means for engaging and moving said cam; and said cam being adapted to engage and move said switch.

References Cited UNITED STATES PATENTS 2,834,851 5/1958 Mastney 335-138 3,310,733 3/1967 Fortune 335-138 3,405,376 10/1968 Giese 335-138 BERNARD A. GILH=EANY, Primary Examiner H. B ROOME, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,539,955 Dated November 10 1970 Inventor(s) John J Nash It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 32, "0 should read c same line, "C should read C line 39, "poriton" should read portion line 40, "adaj acent" should read adjacent Column 5, line 6, "at one time" should read one at a time Column 7, line 37, "causing 11 should read causing cam 11 4" Column 8, line 28, "gorunding" should read grounding line 5 4, current, should read current;

(SEAL) MIQM' I R I Officer (lb-fission 0: Patents FORM PC40 0 0- USCOMMADC c0375 

